How to secure a retaining wall around a hillside pond?

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Hello! And thank you for reading my post.

First let me say, I have NO IDEA what I am doing. Secondly, I need to explain that I am doing this construction without spending any money, if possible.

I have wanted a garden pond for years ~ have been daydreaming about it, trying to decide where on my crazy property to locate it. Out of the blue, I got an offer I couldn't refuse ~ a neighbour with a big tractor would come over and dig my pond for free. Given my landscape obstacles (there are many), my lack of knowledge, the power reading I did last night, and my imagination, I plotted a design for him to excavate on the East side of my house. My house is on the top of a fairly steep hill. I live in Nova Scotia (Canada), Zone 5.

The pond is dug into the side of the hill in the shape of a C (with one side a little longer than the other so that it is not symetrical. The back curve of the C, closest to the house, is dug so that the bottom of the pond drops about 8 feet from the edge of the lawn. The hole graduates to about 1 foot deep at the shallow "legs" of the C. Some of the dirt removed was placed at the "legs" of the C to create a bit of a levee affect. The remainder of the dirt was gradually sloped further down the natural slope of my lawn to marry up with the bottom of my hill.

The "plan" (I use that term loosely) is that the water level of the pond will be approximately 1 foot deep, with a "deeper end" extending to 3 feet deep at the back. So, about 5 feet high of a cliff will extend above the level of the water at the back of the pond, sloping down to a 1 foot "cliff" at the shallow end.

I would like to build a rock wall at the back of the pond. I have accumulated a fairly good pile of rocks from another neighbour's throw-aways (someone thought they might be "bauxlite". I don't know. They break off in straight pieces of you crack them together). At the top of the stone wall I would like to plant things like Cotoniaster and Juniper. I'm thinking this will help prevent erosion?

a) How do I need to approach this cliff? My excavator dude suggested putting in a couple of pressure treated posts behind the rocks. What would the purpose of that be? And is there something else I could use? I thought that pressure treated wood adds bad chemicals to the ground?

b) The rocks will only be at the back of the C. As the cliff becomes lower and lower, is there something I can plant that will adhere to the sides of the earth so they will become root-bound and create a natural retaining wall?

c) The purpose of the pond is to add beauty and joy to my life. I would like to create a waterfall in the rock retaining wall. I'd like to have a few goldfish swimming around in it. I'd like some water flowers/plants. I'd like to attract frogs, peepers, dragonflies, and whatever other critters would enjoy it as their home. Can you have all of these elements in the same pond? Am I absolutely required to have a filtration system for the goldfish or is there a way to create a natural ecosystem that will take care of that on it's own (with my maintenance, of course)?

I'm including a couple of very short videos to help depict what I've tried to explain here.

I would be grateful for any advise you can offer. But please keep in mind my financial constraints. It is now the morning after the dig and I am feeling really nervous about the huge mess in my yard. Have I made a complete mess of things?

Thank you most kindly!
Katie
PS ~ I was not able upload the videos ~ sorry.
 

sissy

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If you are dry stacking the stone the roots from the plants will eventually push the wall ,even if they are cemented that may happen also .Not sure how you would get the liner to lay in that shaped pond with out lots of folds .Interesting shape but not sure how it would work .pics would help a little .Some put the video's on you tube and then post them to here .Pis up slope and down slope and then side view pics would help
 
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Pictures will be a great help. I also would like to see the stone that you have. There is no need for any wood at all behind a stone wall. If the wall is built right then it hold pretty well. The roots that cause the most problems with walls are from large trees not small plantings. Again the wall needs to be built correctly. I would build it dry so it drains well seeing it will be a retaining wall. If I am reading correctly you need a 5 ft wall at the tallest point. That is a tough wall to build with no experience and it could fall on you if not done correctly. I will await pictures. Btw I do this for a living and you will need a lot of stone to do this.
 

sissy

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Being in Canada though I wonder about freeze and thaw with retaining walls .Do you know any one that has one built that you could see it done and how it has held up ..I had an elephant ear 1 year push my retaining wall blocks out and they have a lip on the back of them to hold them in place .But I do have a longer growing season ,so that helped the roots grow fast .
 
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Being in Canada though I wonder about freeze and thaw with retaining walls .Do you know any one that has one built that you could see it done and how it has held up ..I had an elephant ear 1 year push my retaining wall Aquascape UltraKlean filter.blocks out and they have a lip on the back of them to hold them in place .But I do have a longer growing season ,so that helped the roots grow fast .
Not trying to come off to strongly here at all but those retaining wall blocks are terrible and cannot be compared to a well built stone wall. I agree 100% about freezing thus why it should be a dry wall for drainage. I do live in a similar zone. The retaining wall blocks at 5ft will need a different approach then just stacking them.
 
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I realized I could take screen shots of my video, so I am including a couple of pics (not sure if this forum will let me upload more than one at a time, so I may have to follow-up again).

The first pic is simply the outline of the pond before digging. In the pic it looks more like an inverted kidney bean than a C; but the actual hole has longer "legs" on the C than is shown here.

The second picture is me standing in the "deep end" where the rock wall is to go. It is not yet at its full depth of 8 feet in this picture; but you get the idea...... That's a LOT of earth to hold back.

I'll go out and take better pics and will take a picture of the stone. From what you have said RobAmy, I'm guessing I'll need a lot more rocks!
 

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Here is a picture of the rocks. I've included a standard clay brick to show the respective size of the rocks.

The second photo shows the incline of the hill. The deep pool is not visible in the photo.... you can just see where the "level" area drops off as it approaches the steep wall.
 

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sissy

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That may be a little high as most stacked rocks with out support will not hold .I know dry stacked I have done but not over 2 ft tall .I even do dry stacked in front of my filters
 

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I've been reading through other "related" posts and am wondering about creating a foundation for the stone wall out of concrete or salvaged cinder blocks. But then, what would make the concrete "adhere" to the dirt bottom?
 

sissy

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with my retaining wall block I used a foot of crushed granite and tamped it and wet it and tamped it again it is like concrete after all of that .That is over kill here they say but why not since I had it .Footings are usually where your frost line is .Here it is a foot but most go 2 feet .With higher walls they put corrugated pipe with perforations and a soak over it and stone all around it so water runs through it and out the wall freely .They do that here for walls over 5 ft or heavy rains will push dirt into the wall .It can become expensive to build above a certain height .If you can call someone that would help you more for your area .You can even check your local building codes .If a rain comes really hard the whole hillside could let loose being that it is raw right now .I cannot tell the slope but it may not be a good outcome if it does .Concrete in a dirt footing holds up well if done deep enough .Reading about your area footings say 4 ft deep .That could be a lot of cement
 

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That's going to be a great looking pond but I think you'll need much larger, well set rocks for a wall that large. Maybe something like our pond wall, often referrred to as a "rockery" here in the Pacific Northwest...
image.jpg
 
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That was a very nice thing to say, Troutredds! I am sitting here feeling very over-whelmed.... like I need a long nap to make it all go away. I really appreciated your positive spirit!

I have drawn a couple of diagrams to try to depict what I had imagined in my head. Even as I drew them, they seemed impossible. Way too much "cliff" all around. Forgive the poor illustrations ~ they don't show perspective very well.

The picture you included of your "rockery" did give me an idea. Perhaps I should cut out yet even more ground at the back of the C to create more of a slope instead of a cliff. Then I could use the rocks to build a rock garden wall like you have as opposed to a rock wall.

Thoughts?

Really, I have no idea how I should proceed. I just have this big gaping hole in my yard that looks like a big scary mess. Any suggestions are good.

:)
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Troutredds

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I like your alternative idea, Kate. Our rocks start with a slope and end with a five foot vertical wall below the fence. You could start your wall with some larger stones stacked vertically, then cut the slope back more gradually to establish an alpine style rock garden with planting pockets.
 
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Sorry for my late response I was at work. Just take a breath. You have a great design and it will work out. Do not worry about the mess now, all pond demo starts out looking terrible. You will need larger and much more stone to pull off a retaining wall of that size. I do like the idea of more slope. That will make your life easier. If you want the wall it can be done but it will have to be done right without much room for error. The idea of more slope will be more forgiving. You will not need concrete at all. On a hill of that size you may be better off to get someone with a machine to set some larger stones for you at the base, I know that sounds expensive but it might be cheaper then all the additional stone you will need unless the stone is free. If you decide on the wall route let me know and I will try to explain in detail what will be needed to build a safe and good looking wall. The key is to interlock the wall and most people build retaining walls way to thin. To do it right you need to build the base as deep as the vertical face that you see. Think of a triangle effect. The reason for this is so the earth helps hold everything down. This way you kinda know what you will be up against if you go the wall direction. To give you a idea of a dry stack that needs no cement the wall below is about 4ft + on the back side. if I wanted the entire thing to be a retaining wall I would have made the wall thicker at the base. The only thing I may cement is the very top of the wall so it makes a solid cap, this is not needed if you have large enough stones.

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